This is a comparison between the cut broadcast on American TV networks (e. g. Cartoon Network or USwpix) and the uncut Japanese Version.

While other countries have not yet aired Dragonball Kai, the series was already broadcasted a few times in the USA.
In comparison to Dragonball Z you can immediately see that Dragonball Kai was obviously toned down in a few scenes:

Dragonball Z

Dragonball Kai

Additionally, many violent sequences were not even altered for Dragonball Kai, but cut out in the first place. Thus, you will hardly see any close-up shots of Tenchinhan after Nappa cut half of his left arm off. Also, you do not see Freezer's beam going through Vegeta's chest. Even the well known sequence in which Freezer massacres Kuririn is much more harmless than in Dragonball Z.

Getting ready for US-TV:The series was censored in order to be bradcasted on US TV. The censoring reminds one of Naruto's US Version. Sometimes there are cuts which are very noticeable due to a crack in the music, while at other times they used a few tricks, e.g. by retouching things or using alternative material. Sometimes they even altered or postponed soundtracks or sound effects in order to make the cuts less noticeable.

The overall difference in time amounts to 4.5 seconds.
(The rest of the difference in time results from differently long intros.)

0:06Cell gets shredded.
The previous shot runs with less frames per second to make up for the lost footage lengthwise.
no difference

19:21In the US TV Version, the actual hit has been replaced by a white screen (length: 0.04 sec).
no difference